成人体外循环模型中不同压力及流量对动脉滤器排气管分流量的影响

Shunting flow of an open arterial filter purge line in different flow and pressure in a simulated adult cardopulmonary bypass model

目的在常规体外循环管路中存在多条分流路径,其中动脉微栓滤器排气管分流最为常见。本实验通过模拟成人体外循环管路,观测其在不同流量及压力下的分流量和分流率。方法模拟成人体外循环过程,主要包括人工心肺机,变温水箱,成人膜肺和动脉微栓滤器。整个模拟环路采用肝素抗凝血及乳酸林格液预充,使红细胞比容维持在0.21。在模拟体外循环管路中,分别在5种不同流量（流量范围3 000-5 000 ml/min,每次增加500 ml/min）和6种滤器后压力下（压力范围120-220 mm Hg,每次增加20 mm Hg）,记录动脉滤器前、后以及滤器分流管的压力,膜肺前流量和动脉滤器后流量。计算动脉滤器排气管开放状态时分流量,并计算分流率。结果当泵流量不变时,动脉滤器排气管分流率随着滤器后压力增加而升高。当滤器后压力不变时,分流率随着泵流量的增加而降低。当泵流量恒定时,分流管压力随着滤器后压力增加而增加。结论在动脉滤器排气管开放状态下,会产生从动脉管路的分流,分流率过大则会影响患者组织器官的灌注。分流率在低流量和高滤器后压力情况下尤为显著。在滤器后安装流量计有助于精确的了解分流情况。

OBJECTIVE The opening of arterial filter purge line in extracorporeal circuit could cause shunting flow.This study was designed to evaluate the volume of shunting flow by the arterial filter purge line under different flow rates and pressures in a simulated adult cardopulmonary bypass（CPB） model.METHODS The circuit was designed to simulate an adult patient underwent CPB.The extracorporeal circuit was consisted of a heart-lung machine,a heat-cooler system,an adult membrane oxygenator and an adult arterial filter.The circuit was primed with heparinized donor human blood and lactated ringer＇s solution,to keep a hematocrit of 21%.There were 5 different pump flow rates ranging from 3 000 to 5 000 ml/min（500 ml/min increments） and 6 different post-filter pressures from 120 to 220 mmHg（20 mmHg increments）.The pre-oxygenator flow,post-filter flow,the pressure of pre-and post-arterial filter and the pressure of purge line were recorded.The percentage of shunting flow was calculated by the formula.RESULTS When the pump flow was invariable,the percentage of shunting flow from the purge line increased with the increase of postfilter pressure.However,when the postfilter pressure was constant,this trend was opposite.When the pump flow was invariable,the pressure of purge line increased with the increase of postfilter pressure.CONCLUSION Under the opening of arterial purge line,varying volume of blood flow was diverted away from the arterial line.Shunting flow may result in hypoperfusion of the tissue and organs for clinical patients.It is necessary to elevate corresponding blood flow.The flow probe after the arterial filter could monitor real-time arterial flow.